The magnitude of the average electric field normally present in the atmosphere just above the surface of the Earth is about 150 N/C , directed inward towards the centre of the earth .This gives the total net surface charge carried by the Earth to be : $\;[Given \;\in_{0} =8.85 \times 10^{-12} \;C^{2}/N-m^{2} , R_{E} = 6.37 \times 10^{6}\;m\;]$

Question

$(a)\;+670\;kC \qquad(b)\;-670\;kC\qquad(c)\;-680\;kC\qquad(d)\;+680\;kC$